1. Field of the Invention
The present invention is related to a fuel injection device. Specifically, it is related to a fuel injection device used for a diesel engine, injecting fuel supplied at high pressure from a fuel supply source.
2. Related Art
In related art, a fuel injection device injecting fuel has been used for a diesel engine. FIG. 5 is a sectional view of the fuel injection device 101 according to an example of related art. This fuel injection device is provided with the nozzle body 140, the needle valve 110 provided movably forward and rearward in this nozzle body 140, and the injection control valve 120 provided movably forward and rearward in this nozzle body 140 (refer to Germany Patent No. 19512270).
In the nozzle body 140, the first fuel chamber 141, the second fuel chamber 142, the third fuel chamber 143, and the nozzle orifice 145 extending from this second fuel chamber 142 to the outside of the nozzle body 140 are formed. In addition, in the nozzle body 140, the first fuel passage 151 extending from a fuel supply source to the first fuel chamber 141, the second fuel passage 152 extending from the first fuel chamber 141 to the second fuel chamber 142, the third fuel passage 153 extending from the first fuel chamber 141 to the third fuel chamber 143, and the return fuel passage 154 extending from the third fuel chamber 143 to the outside of the nozzle body 140 are formed.
The needle valve 110 can advance and retreat in the second fuel chamber 142, which is biased in the forward direction by the spring 111. This needle valve 110 advances to contact with the needle body, thereby blocking the passage extending from the second fuel chamber 142 to the nozzle orifice 145.
The injection control valve 120 is provided movably forward and rearward in the first fuel chamber 141, the third fuel passage 153, and third fuel chamber 143, which is biased in the rearward direction by the spring 121. This injection control valve 120 retreats to be situated at the first position, thereby allowing the first fuel passage 151 to be communicated with the first fuel chamber 141 and blocking access from the third fuel passage 153 to the third fuel chamber 143. Meanwhile, this injection control valve 120 advances to be situated at the second position, thereby allowing the third fuel passage 153 to be communicated with the third fuel chamber 143 and blocking access from the first fuel passage 151 to the first fuel chamber 141. FIG. 5 shows the state in which the injection control valve 120 is situated at the second position.
According to the above-mentioned fuel injection device 101, when the suppress strength applied to the injection control valve 120 is released, the injection control valve 120 is situated at the first position by the biasing force of the spring 121, and thus fuel supplied from a fuel supply source flows in the second fuel chamber 142 through the first fuel passage 151, the first fuel chamber 141, and the second fuel passage 152. Then, the needle valve 110 retreats to inject fuel, resisting the biasing force of the spring 111 by the pressure of the fuel flowed in the second fuel chamber 142.
Meanwhile, when the injection control valve 120 is pressed to be situated at the second position, fuel stops flowing from the first fuel passage 151 to the first fuel chamber 141, and the fuel already flowed in the first fuel chamber 141, the second fuel passage 152, and the second fuel chamber 142 is discharged to the outside through the third fuel passage 153, the third fuel chamber 143, and the return fuel passage 154. At the same time, the pressure of the fuel flowed in the second fuel chamber 142 decreases, so that the needle valve 110 advances by the biasing force of the spring 111 to contact with the nozzle body to stop fuel injection.
However, the above-mentioned fuel injection device has a problem in which the efficiency is low because the injection control valve is shifted from the first position to the second position to stop the fuel injection operation, which causes most of the fuel already flowed in the nozzle body 140 to be discharged to the outside.